The best nature writing from the newspaper, magazine, blog and book authors of the Lone Star State . . .

Thursday, August 27, 2009

Spiders, Up-close and Personal by Ro Wauer

Spiders have always been fascinating creatures to me! A bit alien, a little scary, but always fascinating. So a recent experience of watching a jumping spider stalk a skipper butterfly truly got my attention. I was first attracted to the skipper that turned out to be a Carus skipper, a new county record, as it feed on gold lantana. Half way through photographing the skipper, I realized that it was being stalked by a jumping spider, a potent predator of butterflies. My attention then shifted to the spider and I watched it edge ever closer to its prey. But apparently I didn’t give the skipper enough credit, because it suddenly flew away to another part of the lantana, and the spider retreated from view.

Jumping spiders are commonplace in Texas. I find them in all sorts of places from flowers and shrubs to various human-made structures, including the deck of my house. They can be tiny, less than a quarter of an inch, to those that reach almost an inch in length. All are rather squat with a head containing mouthparts and eight eyes, a thorax, a thin waist, and an abdomen with eight long hairy legs. All spiders are predators that feed on a huge variety of insects, especially flies and other invertebrates, including other spiders.

Although most spiders are nocturnal in behavior, jumping spiders are daytime hunters. They capture their prey by a stalking and jumping attack; some species can jump twenty times their own length. When sufficiently close, the spider lowers its body, fastens a dragline to the surface, and then leaps onto its prey. A jumping spider detects prey with any of its eight eyes, but it will then zero in with its larger central pair of eyes that are based on long tubes that work like miniature telephoto systems.

Most of the 4500 species of jumping spiders live in the tropics, but North America also has its share. Of the more than 35,000 species of spiders of 105 families, the jumping spider family is the largest. But the cobweb weavers may be more obvious. And the crab spiders may be more noticeable to those of us interested in butterflies. Crab spiders hide among the flowers and grab many an unsuspected butterfly. Although most crab spiders are only about an inch in length, they capture surprisingly large insects, including monarch butterflies.

All North American spiders are venomous, although very few possess venom that can seriously harm humans. The black widow accounts for 50 percent of all recorded spider bites. Black widow and recluse spider venom is neurotoxic, affecting the nervous system, but other spider venom is cytotoxic causing damage primarily to the tissues. Spider venom has been studied for their values of dispersal of blood clots that cause heart attacks and also for use in developing safer kinds of insecticides.

When spider specialist John Comstock of Cornell University was asked “What good are spiders:” he replied “They are damned interesting!” And Paul Hillyard, in “The Book of Spiders,” wrote: “One can find spiders that catch their prey with a sticky globule on the end of a silk line. There are spider architects that construct impressive webs overnight and then take them down again in the morning. One can find caring, responsible spiders that build nursery webs for their families while others carry the whole brood of their back. There are spider engineers, which tunnel into the ground and make secret passages for escape in case of intruders. There is even a unique spider “frogman” which takes down an air supply to breathe underwater. Many species preserve and store food for a rainy day when no flies are about, but some crafty little types have turned to a life of crime and do nothing more than steal food from the webs of their bigger brethren. Still, there is actually one that knocks at the door of another spider’s home and waits for an answer before entering.” But my favorite is the jumping spiders.